Transceiver system



March 4l, 1947.

M. Gl. CROSBY mRANscEIvER sYsTEM FiledFeb. 15', 1943 h NN HQ. w

Patented Mar. 4, 1947 Murray G. Crosby,

Radio Corporation of America,

of Delaware UNITED STATES PATENT oFF1cE- 2,416,1794 'rRANscEIvER sYs'rEM Riverhead, N. Y., assignor to a corporation Application February 15, 1943, Serial No. 475,896

' tions to receive angle modulated carrier Wave energy by means of superregener'ative detection, there being employed an auxiliary network in association With the signal input circuit of the super-regenerative detector to produce angle modulated carrier Wave energy for the purpose of transmitting.

Another important objectv of my invention is to provide an FM carrier wave transceiver system which is economical in its use of electron discharge tubes, and employs a minimum of components whereby it readily lends itself f or compact assembly. v`

Other objects of my invention are to provide' a transceiver system, particularly adapted for receiving either AM or FM signals, which is com pactly constructed and assembled so that the system may be employed as a so-called walkietalkie receiver for military application, or for disposition in mobile units such as tanks, airplanes or marine units wherein space is at a premium.

Still other objects of my invention are to'improve generally the simplicity and efliciency of FM transceiver systems, and more especially to provide an FM transceiver which is not only durable and reliable vin operation, but is economically manufactured and assembled.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims; the in.- vention itself, however, as to both its organization and method of operation will best be un'- derstood by reference to the following description, taken in connection with the drawing, in which I have indicated diagrammatically a circuit organization Whcreby'my inventionfinay be carried into effect.

' In the drawing 11 Claims. (Cl. 250-13) Fig. 1 shows a system embodying the invention,

Fig. 2 graphically illustrates the effect of tube 'I0 on circuit S during signal reception.

Referring now to Fig. 1 of the accompanying drawing, wherein I have shown the circuit diagram of one illustrative embodiment of my invention, the signal collector I is coupled by con-- denser 2 to the high potential side of va signal input circuit S. The signal input circuit consists of coil 3 connectedgin shunt with the adjustable tuning condenser 4. The low potential' side of the signal input circuit S is `established at an .invariable alternating potentiaL. such as ground. `There are provided a pair of electron discharge tubes 5 and 6. Thesetubes are illustrated `as being of the triode type; the invention is not limited to these particular types of tubes. The cathodes of tubes 5 and B are connected to a common lead; the latter is connected to a pre-` determined intermediate tap point 1 on the in-Y put coil 3. The control grids of tubes 5 and 6 are connected in common to the grid terminal of a direct current blocking condenser 8. The

opposite terminal of condenser 8 is connected to the high potential side of input' circuit S. The grid return resistor 9 is connected between the common grid connection of the tubes 5 and z5 and the common cathode connection thereof.

The plate of tube 5 is designated by numeral- I0. on the direct current voltage supply bleeder II through al path which comprises kfilter choke coils I2 and I3, a primary winding I4 ofthe audio output transformer I5, lead I6, switch arm Il` and the adjustable tap I8. The voltage supply bleeder II has one end thereof grounded, while the opposite end is connected to the positive terminal +B of the direct current source. Switch arm lI'I may be adjusted to either of two contact points I8 or 25. Contactpoint I9 is connected to the adjustable slider I8, While contactA point 25 is connected to the positive end of the voltage supply resistor Il. Radio frequency by, pass condensers 28, 2l, and 22 connect the ends of series lter chokes I2 and I3 to ground. -The, network IZ-IS--ZIl-ZI-H functions as a radio frequency and quench frequency filter network to prevent any radio and quench frequency compo-- nents from passing to the primary winding I4. The plate Iil of tube 6 is connected to the lead I6 through a filter network which is similar to4 that just described in Vconnection with the .plate circuit of tube 5. Hence, the series choke coils` are represented by numerals I2'- and'IS', whilei It is connected to a predetermined pointv leak resistors 46 and 4l. sistor'ilt is cross-connected by direct Ycurrent the bypass condensersare designated by nu- Varm 32. The contact points Sl'iand Sll'are the contact points which receive the switch larm 32 in the opposilte position thereof.rv One terminal of switch arm 32 isconnectedto'the vjunction of choke coil I3 and condenser' 22. rIhe other terminal of the switch arm is connected to the.v lower end of primary winding i4.

When the switch arm,.32 is adjusted to contact points 30 and 3i, then the primary winding I4 has one polarity relative to the winding I4. Whenv the switch arm 32 is in the opposite position, then the winding I4 has its polarity reversed. More specically, the former position is the push-push connection for windings i4 and i4', while the latter'is the push-pull connection.`

The secondary winding of Vtransformer i5 is desi ignated by the'numeral l5'. Any desired form of audio utilization network may be connected to the terminals'of winding l5. For example, one orfmo're stages'of audio amplification followed by a-reproducer such as a loudspeaker or head phones may be used. In the case of a walkietalkiefreceiver, lhead phones could bev plugged directly between the ends or winding l5.

The detector tubes 5 and E, byvirtue of their common cathode connection-to the resonant circuit S, function as an oscillating detector system. In other words, the tubes are connected with their input electrodes in parallel in an oscillatorcircuit of the Hartley type. Detection will occurby virtue of grid leak detection, because of the condenser 8 and grid leak resistor 9. Superreg'enerat'ive detection action is secured by means ofthe quench oscillator network now to 'be described. y e

The quench oscillator circuit comprisesva pair of electron discharge tubes which are designated by-numerals 4I! and 4 l and these tubes are shown as triodes by way of illustration. For the sake of `compactnessof construction both tubes 4u and 4l maybe mounted within a single tube envelope, as 1, in the case of the well-known twin triode type ci i tube. This may also be true in the Vcase ofthe tubes 5 andl 5. The plates 42 and 43 of 'tubes 40 and4 i-respectively are connected to opposite sides of a resonant tank circuit comprising coil 44, shunt tuning condenser 45 and condensers 263-20.

. The cathodes of tubes 49 and 4| are connected in common to ground, while the control grids are connected to ground through respective grid The grid end of reblocking condenser 46 to the plate 43, while the direct current blocking condenser 4l' connects plate 42 to the 'grid end of resistor 41.

.iusted over the voltage supply resistor 54. The latter has one end thereof grounded, while the opposite end thereof may be connected to the positive terminal -I-Bcf the direct current source. Y

' therewith provide a push-pull type of oscillator.

The latter applies its oscillatory output energy in alternating fashion to the plates lo andv It or" detector tubes 5 and 6 respectively. Thus, one end of `coil 44 is coupled by means of the direct current blocking condenser iii! to plate It, while the direct current blocking condenser 6i connects plate I0' to the opposite end of coil 44.

'When the switches l'I-IS and Sil-52 are closed, then the tubes 5 and 6 function in the mannerof La super-'regenerative detector. The signal collector device I may be a relatively short rod,as is customary in the case of mobile compact receivers, or it may be a dipole unit. The signal :circuit S, in the case of reception of FM signals, will be tuned to the mean frequencyFc ci the desired FM transmitter. 'I do not wish to'restrictthe present invention to any particular band ofA reception, since the invention will function to receive FM signals in any of the megacycle In the usual `form of prior FM detectorcircuit there has been employed a pair of input circuits oppositely mistuned relative to the mean frequency of received FM signals. There has, also, been utilizedy a phase shift net* work to provide frequency discrimination. `In

the present system I provide a form of sweep frequency discrimination under the control of the quench oscillator.

In other words, the tuning instrumentality 4 islinitially adjusted, assuming that quench oscil-` energy. The alternately applied quench energy from .the .quench oscillator is then employed altern The plates 4-2 and 43 arejconnected to a commonsourceof direct current voltage by means of a 'lead 43. The latter has one end thereof connected to the midpoint 49 on coil 44. VThe 3 opposite end of lead 48 is connected to an adju'stab'le switch element 5) which is adapted to be'adjusted toeithercontact point '5I `or contact Vpoint :52.Y TheV contact point 52 may be'connectedto a lvoltage slider 53 adapted to bead-- nately, and `according to a predetermined sequence, to shift the reactive eilect produced bya reactance tube l0. The latter acts to detune the circuitv S ata superaudible rate to either sideof the mean, or normal, frequency ofcircuit S. During reception of FM signals the plates It! and l0' .of the super-regenerative ,detector tubes 5 and 6 are in. push-pull relation. That is, switch 32-3!-30' is closed. Should AM carrier signalsY bereceived, then theswitch arm132 would be adjusted to its opposite position so that the windings I4 and I4V would be of such polarity that the plates Il! and I would ybe connected in push-push fashion. y Y

Returning to the reactance tube l0, the latter is illustratively depicted as of the pentode type. It may be a simple triode tube. The cathode 'il is connected to ground through the usual grid biasing network l2, while the plate '73 is connected to a point of positive potential +B through the radio frequency choke coil 74. The lower end of coil 'I4 is bypassed to ground by ccndenser 15. Plate 73 is coupled to the high potential side of circuits by condenser 76. It is, also', connected to the control grid l? by means of the direct current blocking condenser 18. The grid return `resistor 'I9 connectsV grid ll to an adjusti able slider of potentiometer 8l'. One end of ground. Condenser 82 is connected between the upper end of slidable arm 88 and ground. The opposite end of resistor 8l is connected to switch arm 83 which is ladapted to be adjusted to either ofV contact points 84 or 85. Switch 83-85 is closed during reception ofV signals. In the closed position of the switchthe coupling condenser 86 connects contact point 85 to the coil 44 of the quench oscillator.

' The contact point 84 is connected to ground through the secondary winding 98 of a modulaV tion input transformer 9|. The primary winding 92 of transformer 9| has one end thereof connected to the input microphone 93. The opposite terminal of the microphone is connected to the opposite end of winding 92 through a negative biasing voltage source 94. The tube 1li-produces a capacitative effect across the resonant circuit S by virtue of the phase shifter network 1 8-19. As is well known to those skilled in the art, there is developed across resistor 19 alternating voltage which is in phase quadrature with the alter.- nating voltage existing at plate 13 of tube 18.

This is due to the fact that condenser 18 and resistor 19 are arranged in series between plate 13 and cathode 1I, and the magnitude of resistor 19 is low compared to the reactance of con denser 18. Under these conditions the plate to cathode impedance of tube 10, which is in shunt across Vresonant circuit S, produces a capacitative reactance effect across the resonant circuit S. The magnitude of the reactive effect is a function of the transconductance of tube 18. Since the quench oscillatory energy is applied to the grid 11 of tube 1Q when switch 83--85 is closed, it follows that the gain of tube will vary at the superaudible frequency rate of the quench oscillator. Hence, the reactive effect of tube 10 across resonant circuitl S will vary at the same superaudible rate. Of course7 the invention is not limited to the production of a capacitative reactive effect across S, since the effect could be inductive by a proper change in the phase shifter network.

Considering, again, the application of the f quench oscillations to detector tubes 5 and 6 in alternate manner, it will be clear that when quench oscillations are applied, for example to tube 5, the same oscillatory quench energy at that instant will be applied to grid 11 of reactance tube 18. Thus, there will be produced a capacity effect across input circuit S of such a value that they resonance curve of circuit S will be shifted to one side of the mean frequency Fc of incoming FM signals. On the other hand, when the quench oscillator applies its oscillatory energy to the o-pposite tube 5, the reactance tube 'Ill will be caused to produce concurrently a capacity effect across input circuit S such that the resonance curve of the latter will now shift to the oppositeV side of the mean frequency of the FM signals. In Fig. 2, which is self-explanatory, this action is graphically depicted. There is produced the same effect as would be the case were each of tubes 5 and 6 provided with its own respective input circuit, and the input circuits were oppositely and equally mistuned relative to the mean frequency Fc of incoming FM signals.

In other words, the quench oscillator is em# ployed to control the reactive effect produced by tube 1!) in sucha manner that sweep frequency discrimination occurs at input circuit S thereby to provide the required conversion of the FM signalsI into corresponding AM signals. The-latter are readily rectified by the Vsuper.-regenerative detector tubes 5 and 6, assuming the plate circuits are connectedin push-pull relation. Reference is made to my copendng application Serial No. 446,876, led June 13, 1942, particularly Fig, 4, for a more detailed explanation ofthe functioning of a "sweep frequency discriminationnetwork of this type. l

Should the receiver be employed to receive AM carrier energy it would only be necessary to throw' switch 32 into push-push position. That is, switch 32-38-3! is closed. The tuning means 4 would then be adjusted so as to tune circuit S to thecarrier frequencyof the incoming AMsignals. Super-regenerative detection would be provided by virtue of the application of the quench oscillations in alternate fashion to the plates I9 and I0. AM vdetection would not be affected by the sweep action of the reactance tube 10', because the mean frequency of circuit S would be the AM carrier frequency. For a somewhat more selective type of AM reception switch 83 may be opened to prevent the variation of the capacity effect of tube 10 by the quench oscillator. In other words, tube 10 may be in or out of'circuit with resonant circuit S for AM reception.

The receiver is readily transformed into a transmitter of FM signal energy by simultaneously adjusting switch arms 83, 58 and l1 into contact with respective contact points 84, 5I and 25 respectively. When switch 83`84 is closed, the reactance tube is under the control of an audio modulation'source. The audio modulation source comprises any desired type of microphone 93 whichis connected across the primary winding 92 of input transformer 9L A negative, biasing source Mis included in circuit with the microphone. lThe secondary winding 99 is connected between contact point 84 and ground. The audio modulation sourcel has its 'modulation voltage applied to 'control grid 11, and the plate to cathode impedance of tube 1li will have its magnitude varied in accordance with the intencity and frequency rate of the audio modulations. In this case the circuit S functions as the oscil lator tank circuit of tubes 5 and B; These tubes now` function as oscillator tubes having parallel gridswith plates grounded'for radio frequency currents. Switch {1 -25 applies sufficiently high positive potential to the, plates of these tubes so that they readily act as oscillators.- In the v-reception position of switch arm I1, the slider I8 has been adjusted to reduce the high voltage to be applied to plates lil-l0.

Opening of switch 59-52 renders the quench oscillator inoperative. The oscillations devel oped across circuit S will bevaried in frequency in accordance with the amplitude of the audio modulation voltage from source 93 and the rate of frequency variation will be a functiono'fthe modulation frequencies per se. It will be recognized that the frequency modulation process per se is of a type Well known to those skilled in the art. If desired, the switch arms 83, I1 and 50 can be mechanically coupled for unicontrol adjustment. The frequency modulated oscillations developed at circuit S are radiated from the antenna I When transmission is employed the switch arm 32 may be left wherever it is, since 'it does not affect the tubes 5 and 5 during transmission. d There are several advantagesy secured by this transceiver system. Super-regeneration 'is employed for either AM or FM signal reception. This means that high gain will be securedV with weak signals fed tothe detectors. 'The-'quencl'f energy is. applied to. the detector plates. This prevents spurious oscillations that wouldv other- Wise arise if the quench energy Were applied to the detector grids. The AM reception may proceed even with tube 'l0 in circuit; it is only necessary to throw switch arm 32 `into push-push position. This means that a minimum of operational adjustments are required inthe eld. For transmission it is merely required to actuate a common actuator for the switch arms SS--I 1.

The very Vsame reactance tube lli and detector tubes 'and 6 may thenbe employed to transmit. Thisis highly advantageous from the viewpoint of economy of parts, space and weight. I f While I have indicated and described a system for carrying my invention into effect, it will be apparent to one skilled in the art that my invention is by no means limited to the particular system shown and described, but that many modilcations may be made without departing from the scope of my invention as set forth in the appended claims. What I claim is: 1 1. In a transceiver system, at least one electron discharge tube having a resonant signal input circuit, regenerative connections between the, output and input electrodes of said tube, said connections including said resonant input circuit, a quench oscillator for applying superaudible irequency quench oscillations to an electrode of said tube, a modulation output circuit coupled to the output electrodes of said tube, a second electron discharge tube having its plate to cathode impedance connected across said resonant input circuit, means'electrically associated with said second tube to cause said impedance to' simulate a reactance across the resonant circuit, means applying said quench oscillationsY from said quench'oscillator to an electrode of said second tube thereby tovary the magnitude of said reactance at said superaudible rate, a source of audio modulation energy, k:means for selectively rendering said quench oscillator inoperative, means for selectively'rendering said first tube operative as an oscillator, and means for selectively disconnecting said second tube from the quench oscillator vand connecting rthe second tube to said audio modulation source.

2. In a transceiver system for frequency modulated carrier wave energy, a pair of electron discharge tubes having a common signal input circuit adapted toV be tuned to a desired carrier frequency, regenerative circuit connections between said tubes and said common input circuit, a modulation output circuit coupled'to the'output electrodes of said tubes, a quench oscillator adapted to produce oscillations at a superaudible frequency, means for applying said quench os-v cillations to the output electrodes Vof said tubes in alternate mannerv thereby to provide superregenerative detectionby said pair of tubes, a reactance tube having its cathode to plate impedance connected in shunt across said input circuit, means applying said quench oscillation energy to said reactance-tube thereby to vary the magnitude of said Yimpedance in a sense, and at a rate, such as to permit said signal input circuit to function as a discriminator of applied frequency modulation signals, a source of audio modulation signals, means for selectively .coninecting the said modulation source to the reactance tube and simultaneously disconnecting the latter from Ythe quench oscillator, means rendering the quench oscillator ineffective, and additional means for. rendering'said pair of tubes op- 8 erable as oscillator tubes in response to connection of said audio modulation source to the reactance tube.

3. In combination with a super-regenerativel detector `circuit of the type comprising a pair of super-regenerative 'detector tubes having a common resonant input circuitand a quenchoscillator for applying quench oscillations 'to said' pair of tubes; the improvementwhich comprises means for converting said super-regenerativey de tector tubes into a carrier oscillator, a reactance tube electrically associated with said resonant signal circuit for producing frequency variation of carrier oscillationsproduced by the carrier oscillator, an audio modulation source for varying the efiect of said reactance tube, and means for rendering said quench oscillator ineifective when said detector tubes function as said oscillator.

4. In combination, in a radio signalling system having a resonant signal input circuit, an oscillating detector fed by said input circuit, a quench oscillator for applying quench oscillations to the detector, means for converting said'detector into a carrier oscillator, a reactance tube electrically associated with said resonant signal circuit vfor producing frequency variation of carrier oscillations produced by the carrier oscillator, an audio modulation source for Varying the effect of said reactance tube, and means for rendering said quench oscillator ineffective when said detector functions as a carrier oscillator. y

5. In combination with a super-regenerative detector having a resonant input circuit and a quench oscillator for applying quench oscillations to the detector; the improvement which comprises means for converting said super-regenerative detector into a carrier oscillator, a reactance tube connectedwvith said resonant signal circuit for producing frequency Variation of carrier oscillations, Va source of modulation signals for varying the effect of said reactance tube, and means for rendering said quench oscillator ineiective when said detector functions as a carrier oscillator.

6. In a transceiver system, a detector having a resonant signal circuit, regenerativeconnections between the detector output and input, said connections including said resonant signal circuit, a quench oscillator for applying quench frequency oscillations to the detector, a modulation output circuit coupled tothe detector, an electron discharge tube having its plate to cathode impedance iconnected'across said resonant circuit,

' means connected with said tube to cause said impedance to simulate a reactance across the resonant circuit, means applying said quench oscillations from said quench oscillator to an velectrode of said tube thereby to vary the magnitude of said reactance, a source of modulation signal energy, means for selectively rendering said quench oscillator inoperative, means for selectivelyrendering said detector operative as a carrier oscillator, and lmeans for selectively disconnecting said tube from the quench oscillator and connecting the tube to said modulation source.

7 In a ltransceiver system, at least one electron discharge tube having a resonant signal input circuit, regenerative connections between the output and input electrodes ofsaid tube, said connections including said resonant input circuit, a quench oscillator for applying superaudible frequency quench oscillations tothe anode electrode of said tube, a modulation output circuit coupled to the anode electrodeof said tube, a second electronv discharge tube having its plate to cathode impedance connected across said resonant' input circuit, means electrically associated with said second tube to cause said impedance to simulate a capacitative reactance across the resonant cir-- cuit, means applying said quench oscillations from said quench oscillator to a control electrode of said second tube thereby to vary the magnitude of said simulated reactance at said superaudible rate, a source of audio modulation energy, means for selectively rendering said quench oscillator inoperative, means for selectively rendering said first tube operative as an oscillator, and means for selectively disconnecting said second tube from the quench oscillator and connecting the second tube lto said audio modulation source.

8. In a transceiver system, a pair of electron discharge tubes having a common signal input circuit adapted to be tuned to a desired carrier frequency, means -alternately effective on said tubes to cause the latter to provide super-regenerative detection, a reactance tube having its cathode to plate impedance effectively in shunt across said input circuit, means responsive to said alternately effective means to control said reactance tube thereby to vary the magnitude of its impedance in a sense, and at a rate, such as to permit said signal input circuit to function as a discrimnator, a source of audio modulation signals, means for selectively Iconnecting the said modulation source to the reactance tube,v and additional means for rendering said pair of tubes operable as oscillator tubes in response to connection of said audio modulation source to the reactance tube.

9. In combination with a super-regenerative detector circuit and a signal receiving antenna coupled thereto, means for converting said superregenerative detector into a carrier oscillator, a reactance tube electrically associated with said f a super-regenerative detector, means for converting said detector into a carrier oscillator, means .electrically associated with said resonant signal circuit for producing frequency variation of carrier oscillations produced by the carrier oscillator, an audio modulation source for varying the effect of laid last means, and means for rendering said rst means ineffective when said detector functions as a carrier oscillator.

11. In combination with a super-regenerative detector having a resonant signal input circuit, means for converting said super-regenerative detector into a carrier oscillator, means connected with said resonant signal input circuit for producing frequency variation of carrier oscillations, and a source of modulation signals for varying the effect of said means.

MURRAY G. CROSBY.

REFERENCES CITED The following references are of record in the file of this patent:r v p UNITED STATES PA Number Name Date 1,607,485 Schmidt Nov. 6, 1926 2,082,317 Barber Junel, 1937 2,018,569 Pettengill Oct. 22, 1935 

